Not Applicable
Not Applicable
This invention relates to a process for the recovery of coffee aroma prior to extraction and to the aroma so recovered. The recovered aroma is useful for aromatizing instant coffee.
Aromas are an important part of many products since consumers associate certain aromas with certain products. If the product lacks the aroma associated with it, consumer perception of the product is adversely affected. This is particularly a problem in the field of instant coffees, although it also exists in other fields. Instant coffee powders which are obtained from commercial processes involving extraction, concentration and drying, are usually substantially aroma-less. For this reason, it is conventional to recover coffee aromas which are given off during the processing of the instant coffee and to reincorporate these aromas into the concentrated coffee extract prior to drying or into the instant coffee powder.
The coffee aromas are recovered at several points during processing of the instant coffee and most commonly during grinding of the roasted beans and by steam stripping of the coffee extract prior to concentration and drying of the coffee solids.
The recovery of aroma from ground coffee is disclosed in U.S. Pat. No. 3,535,118. This patent discloses a process in which roast and ground coffee is placed in a column and maintained at about 40xc2x0 C. The bed of coffee is then moistened by spraying water on it to assist in displacing aromas from the coffee particles. An inert gas, usually nitrogen, is heated to about 44xc2x0 C. and introduced into the column from beneath the bed. As the inert gas passes up through the bed, it strips the aromas from the coffee particles. The inert gas is then fed to a condenser which is operated at a temperature of about 50xc2x0 C. to condense water in the inert gas. The de-watered inert gas is ultimately fed to a cryogenic condenser to condense the aroma as a frost. The frost is then recovered.
Another process for recovering aroma from roast and ground coffee is described in international patent application WO 97/10721. In this process, the ground coffee is transported through an elongated mixing zone while being agitated. At the same time, an aqueous fluid is sprayed into the elongated mixing zone to moisten the ground coffee as the ground coffee is being transported and agitated. Aroma gases released by the moistened ground coffee in the elongated mixing zone are drawn off and are collected. A similar processes are described in UK patent 1,466,881 and U.S. Pat. No. 4,092,436.
One of the problems perceived to arise with these processes is that they results in pre-wetting of the coffee grounds outside of the extraction cell or column. According to Sivetz, M and Desrosier N. W.; 1979; Coffee Technology, AVI Publishing Company, Inc., page 334, this practice is bad because it xe2x80x9ccauses staling of ground coffee in less than an hour, accompanied by a heavy, undesirable flavor and a loss in natural coffee volatilesxe2x80x9d. Sivetz and Desrosier strongly advocate that first wetting of the coffee grounds should occur in the extraction cell or column. Consequently recovery of aroma from ground coffee by pre-wetting it is not common practice; despite ground coffee being a good source of aroma.
Further, not all components of the aroma obtained in a cup of freshly brewed coffee are captured during pre-wetting. Consequently, unless further aroma is captured later during the process, some aroma components are lost; components which would, if incorporated into instant coffee powder, improve the aroma of a beverage prepared from the instant coffee powder. Further, many of the conventional recovery techniques damage or alter the aroma components.
Therefore there is still a need for a process for recovering aroma from ground coffee.
Accordingly, in one aspect, this invention provides a process for the recovery of aroma components from coffee, the process comprising:
providing a slurry of coffee grounds in an aqueous liquid;
stripping aroma components from the slurry using gas in a substantially counter-current manner for providing an aromatized gas containing aroma components; and
collecting the aroma components from the aromatized gas.
The process provides the advantage that significantly larger amounts of aroma components may be stripped from the coffee than is the case with conventional processes. Further, since the aroma components are stripped from the coffee prior to extraction, thermal degradation of the aroma is reduced to a minimum. Also, these aroma components may be readily reincorporated to provide a soluble coffee product which has increased and improved aroma and flavor.
The slurry of coffee grounds may be provided by slurrying roasted and ground coffee with the aqueous liquid, or by slurrying whole coffee beans with the aqueous liquid and then subjecting the coffee beans to grinding. The coffee grounds preferably have an average particle size in the range of about 1 mm to about 3 mm.
The process preferably further comprises the steps of adding the collected aroma components to a concentrated coffee extract and drying the coffee extract to powder for providing an aromatized soluble coffee powder.
The process may further comprise the step of concentrating the collected aroma components.
The aroma components may be collected by subjecting the aromatized gas to one or more condensation operations. Preferably, in a first operation, the aromatized gas is subjected to condensation at a temperature in the range of about 0xc2x0 C. to about 50xc2x0 C. and, in a second operation, the aromatized gas is subjected to cryogenic condensation at a temperature of less than about xe2x88x9280xc2x0 C. The first operation may be carried out in one or more steps. For example, the aromatized gas may be subjected to condensation at a temperature in the range of about 80xc2x0 C. to about 95xc2x0 C. and, in a second step, at a temperature in the range of about 0xc2x0 C. to about 10xc2x0 C. Alternatively, the aromatized gas may be subjected to condensation at a temperature in the range of about 20xc2x0 C. to about 50xc2x0 C.
Preferably the aroma components are stripped from the slurry in a disc and donut stripping column. The gas used to strip the aroma components is preferably low pressure gas; for example steam at a gauge pressure of less than about 100 kPa.
In another aspect, this invention provides an aromatized, spray-dried soluble coffee powder which comprises least about 0.35 equivalent xcexcg/g furans and at least about 0.25 equivalent xcexcg/g diketones.
In yet another aspect, this invention provides an aromatized, freeze-dried soluble coffee powder which comprises least about 0.60 equivalent xcexcg/g furans and at least about 0.40 equivalent xcexcg/g diketones.
The invention also provides aromatized soluble coffee powders produced by the processes defined above.